Our specific research goal for this coming year is to purify the smallest component of enterobacterial common antigen(s) which retains immunogenicity and hopefully gives rise to protective antibodies, as contrasted to a purified component which may be only serologically reactive. Our success in being able to determine the anatomical locus of enterobacterial common antigen (Kunin) in this past year will be most helpful in the ultimate purification of the antigen(s). Since no purified antigenic component has yet been obtained which remains immunogenic, it is of great interest to obtain a purified and chemically defined common antigen(s) which is immunogenic in order to define more precisely the role of enterobacterial common antigen(s) antibodies in protection. The evidence thus far obtained suggesting that antibodies against enterobacterial common antigen (Kunin) elicit protective activity in experimental pyelonephritis, has far-reaching implications. The isolated and purified enterobacterial common antigen (Kunin) may eventually have unlimited application by serving as a useful immunogen for conferring immunity to a variety of enterobacterial infections. The bewildering number of antimicrobial agents and various recommendations for dosages and duration of therapy together with the continuous introduction of new agents, perhaps serve to emphasize the shortcomings of chemotherapeutic agents available for the treatment of urinary tract, gastro-intestinal and noscomial infections caused by Enterobacteriaceae. Exploring the possibilities of vaccine therapy in view of the important role of these organisms in infections of both man and animals, appears greatly warranted. If the purified enterobacterial common antigen (Kunin) antibody provides protective effects in experimental animals, an analogous situation may very well exist in the human. BIBLIOGRAPHIC REFERENCES: Dominigue, Gerald J., and Emmett Johnson, The Common Antigen of Enterobacteriaceae and its Biologic Significance. The Immune System and Infectious Diseases. 4th Int. Convoc. Immunol., Buffalo, N.Y., 1974, pp. 242-262 (Karger, Basel 1975). Johnson, Emmett J., Gerald J. Domingue, and Gloria D. Klein, Anatomical Locus of the Common Enterobacterial Antigen, accepted for publication by Zeitschrift fur Immunitatsforschung, 1976.